Jim Jennings

I have an interest in clocks, secondary to my interest in steam locomotives. In about 1995, after constructing two steam locos, I thought about making a simple clock (or more correctly, a time-piece). It had to be weight-driven, go for a week between windings, and be suitable to hang on a wall (so that vibrations from loose floor boards wouldn’t affect the time-keeping). It also had to look like a clock and be easy to read the time. This ruled out a skeleton clock.

I discovered that John Wilding had designed such a time-piece, and had put all the instructions for construction into book form. After purchasing said book at great expense (then £7.25), I read it and decided that construction would be within my limited capabilities, although I would have to adapt my lathe so that I would be able to cut gear wheels. I would also need to learn a new vocabulary, as clock-makers used terms which were foreign to me.

First of all, I made a simple dividing head so that I could cut the teeth around the wheels. This was designed by L. C. Mason, and uses the Myford change wheels (see photograph; the set-up you see is to cut 44 teeth). This I found most satisfactory. It gave me all the divisions I  required, apart from 64, as this needed two 40-toothed wheels. Fortunately, a fellow Bradford Society member had a large 64-toothed wheel which he no longer required which he donated to the Jennings Benevolent Repository. I used this by indexing every tooth.

A simple cutting frame was necessary which held cutters made from silver steel for cutting the (gear) wheels, and was designed to rotate at about 4,000 rpm. It was driven by a pulley and belt from my pistol drill arranged behind the lathe bed. This was superseded by a (purchased) milling spindle which was mounted on the vertical slide and driven by an external electric motor. See photograph.

The other item was a depthing tool which I have either lost or given away. This is used to plant the wheels and pinions at the correct distance apart to ensure smooth running of the clock.

These two items were the main additions I had to make in order to begin construction; learning the new vocabulary came about gradually as I worked my way through the book. A few of the terms are: pinion (small gear wheel with up to 20 teeth); pitch circle, diametral pitch, addendum (terms used to describe {gear} wheels); leaf (individual tooth of a pinion); spandrel (not to be confused with Spangles, which were square, fruit-flavoured sweets, traditionally sucked while watching films in the cinema, but decorative brass castings at each corner of the dial); chapter ring (the broad ring of metal on the dial on which are engraved the numerals), and cartouche (the engraved

plate on the dial which shows the maker’s name).

I think the above gives an indication of the learning curve I had to negotiate when I changed jobs from locomotive engineer to horologist – but if I could do it, I’m sure anyone else could do likewise.